Valmiki Ramayana Bala Kanda Sarga 19 Shloka 11
Original Shlokaन च तौ राममासाद्य शक्तौ स्थातुं कथञ्चन।।1.19.11।। न च तौ राघवादन्यो हन्तुमुत्सहते पुमान्।
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तौ Maricha and Subahu, रामम् Rama, आसाद्य having reached, कथञ्चन in any way, स्थातुम् stand, न शक्तौ not be able, राघवात् except Rama, अन्य: any other, पुमान् man, तौ both of them, हन्तुम् to slay, न उत्सहते will not be capable.
Both of them (Maricha and Subahu) will not be able to withstand Rama in any way. Rama, and Rama alone, is capable of destroying them.